Meanwhile, the Food Standards Agency (FSA) has announced results from 1, 133 new tests on beef products.
Fellow supermarket chains Rewe and Tengelmann said they are examining certain beef products as a precaution.
It's the latest twist in a Europe-wide crisis over rogue horse meat in beef products.
The US still has a ban on British beef products, which was imposed in 1997.
The Food Standards Agency now wants the industry to test all its processed beef products.
Other German retailers including Tengelmann and Rewe are now checking their processed beef products too.
The amendment would require exporting countries to certify that their beef products were free from BSE.
The grocery industry will be asked to introduce a voluntary withdrawal of European beef products.
Horsemeat has been found in a number of processed beef products across Europe, raising questions about the food chain.
Concerns about food standards were sparked after horsemeat was found in a number of processed beef products.
Lancashire County Council leader Geoff Driver said the council had "no choice" but to withdraw all beef products.
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Preliminary tests have found six new beef products that may contain horse DNA, the Food Standards Agency says.
Iceland said that all of its own brand beef products have been found to be free from horsemeat.
The company has admitted that test results from 29 January showed traces of horsemeat in its beef products.
With prices higher in America, Canada's exports of boxed beef and beef products have surged to record levels.
Schools, hospitals, chain and fast-food restaurants, have all been serving horse meat in their beef products without realizing it.
Findus said on Friday that it had tested all its other beef products and found no evidence of contamination.
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They also found three beef products with pig DNA above a 1% threshold.
But that has now been extended to other beef products, such as mince.
The agency says figures are not currently available for cases of trace contamination of other species found in beef products.
Police in the Irish Republic were asked to investigate after horsemeat was found in beef products at a third factory.
Traces of horsemeat have also been found in numerous processed beef products across Europe, including in France, Switzerland, Sweden and Germany.
The council is no longer putting mince beef products supplied by Welsh Bros Ltd on the menu at its care homes.
The scandal began in Ireland in mid-January when the country announced the results of its first-ever DNA tests on beef products.
Owen Paterson said he was "pleased" with the plans, adding it was "wrong" consumers had bought beef products that contained horse.
The deadline for initial tests on processed beef products was Friday, and horsemeat was found in just over 1% of samples.
No horse or pork DNA has been found in tests carried out on beef products taken from a North Yorkshire firm.
The company, part of the John Lewis Partnership, said it would be creating a new facility to supply its own beef products.
It comes after Staffordshire County Council, which provides meals to 87% of its schools, decided to take beef products off its menus.
Since then beef products containing horsemeat have been found in a number of European countries, including France, Norway, Austria, Switzerland, Sweden and Germany.
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